A high speed near infrared photometer for lunar occultation studies

A recently developed near infrared high speed photometer intended for lunar oc-cultation studies is described. The primary scientific objective is to reach milli arc second levels of angular resolution so that circumstellar structure of the occulted sources can be resolved. Near infrared sky brightness close to the lunar limb is also studied. Angular diameter derived from the observed occultation of IRC +20169 is presented and system performance discussed.     

Massive disks in low surface brightness galaxies

An update of the set of low surface brightness galaxies is presented which can be used to set constraints on the otherwise ambiguous decompositions of their rotation curves into contributions due to the various components of the galaxies. The selected galaxies show all clear spiral structure and arguments of density wave theory of galactic spiral arms are used to estimate the masses of the galactic disks. Again these estimates seem to indicate that the disks of low surface brightness galaxies might be much more massive than currently thought. This puzzling result contradicts stellar population synthesis models. This would mean also that low surface brightness galaxies are not dominated by dark matter in their inner parts. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cross-Calibration and Long-Term Monitoring of the Microwave Radiometers of ERS, TOPEX, GFO, Jason, and Envisat

The radiometers on board the satellites ERS-1, TOPEX/Poseidon, ERS-2, GFO, Jason-1, and Envisat measure brightness temperatures at two or three different frequencies to determine the total columnal water vapor content and wet tropospheric path delay, a major correction to the altimeter range measurements. In order to asses the long-term stability of the path delay, the radiometers are calibrated against vicarious cold and hot references, against each other, and against several atmospheric models. Four of these radiometers exhibit significant drifts in at least one of the channels, resulting in yet unmodeled errors in path delay of up to 1 mm/year, thus limiting the accuracy at which global sea level rise can be inferred from the altimeter range measurements.     

一种Brovey变换图像融合法的改进算法

分析了的Brovey变换融合算法,提出了一种新的基于Brovey变换、对数变换亮度调整的图像融合方法,试验数据的对比和分析证明了其保留多光谱影像的光谱信息.     

基于遥感和GIS的哈尔滨城区热岛效应研究

本文利用遥感和GIS技术对LandsatETM 热红外遥感数据进行处理,反演市区的地面亮温,并进行正规化处理和等级划分,研究城市热岛的时空变化规律和温度场的空间分布规律,揭示城市热岛效应空间格局。通过对哈尔滨市区热岛效应分析,可以确定城区内热岛效应的分布及监测城市化进程,为城市热环境质量评价和热源调查提供准确、丰富的信息。     

Verification and recalibration of HY-2A microwave radiometer brightness temperature

HY-2A is the first one of the Chinese HY-2 ocean satellite series carrying a microwave radiometer(RM)to measure sea surface temperature,sea surface wind speed,atmospheric water vapor,cloud liquid water content,and rain rate.We verified the RM level 1B brightness temperature(T B)to retrieve environmental parameters.In the verification,TB that simulated using the ocean-atmosphere radiative transfer model(RTM)was used as a reference.The total bias and total standard deviation(SD)of the RM level 1B TB,with reference to the RTM simulation,ranged-20.6-4.38 K and 0.7-2.93 K,respectively.We found that both the total bias and the total SD depend on the frequency and polarization,although the values for ascending and descending passes are different.In addition,substantial seasonal variation of the bias was found at all channels.The verification results indicate the RM has some problems regarding calibration,e.g.,correction of antenna spillover and antenna physical emission,especially for the 18.7-GHz channel.Based on error analyses,a statistical recalibration algorithm was designed and recalibration was performed for the RM level 1B TB.Validation of the recalibrated TB indicated that the quality of the recalibrated RM level 1B TB was improved significantly.The bias of the recalibrated T B at all channels was reduced to<0.4 K,seasonal variation was almost eradicated,and SD was diminished(i.e.,the SD of the 18.7-GHz channel was reduced by more than 0.5K).     

2020年新疆于田Ms6.4地震前热红外亮温异常研究

获取了2020年4-7月新疆于田Ms6.4地震区周边约400 km范围内连续的中国气象卫星FY-2G遥感热红外资料,选取北京时间凌晨1:00～5:00时的分钟值数据,经过小波变换和功率谱估计法进行处理,得到研究区地震前后相对功率谱异常演化过程,对比分析了 2019年相同频率同期的相对功率谱幅值,并讨论了异常时间演化过程...     

COOLING RATES, SKY VIEW FACTORS AND THE DEVELOPMENT OF INTRA-URBAN AIR TEMPERATURE DIFFERENCES

Intra‐urban cooling rates were monitored for a year in the centre of Göteborg on the Swedish west coast. Five sites with different building geometry ‐ from dense canyon to open space ‐ within a radius of 300 m were analysed. Results showed two modes of cooling during the night. In the first mode, the cooling was site‐dependent ‐the open space cooled the most and the dense canyon the least. In the second mode, which began about 3–4 hours after sunset, all sites cooled at the same rate. Our hypothesis is that in the early part of the evening both radiative divergence and sensible heat dominate the cooling. However, as the evening progresses, a spatially homogeneous inversion is established which controls the radiative cooling, making the cooling independent of both surface geometry and surface type. From April to November the sites cooled rapidly around sunset and the cooling slowly decreased during the rest of the night. However, between December and March, the cooling was less intense, with an almost constant rate during the entire night. It has been suggested that this might be the result of the draining of stored solar heat during the summer and a continuous flux of anthropogenic heating during the winter.     

Estimation Of Sensible Heat Flux From The Surface Temperature Wave And One-Time-Of-Day Air Temperature Observation, Part Ii – Heterogeneous Surfaces

By means of the algorithm presented in Part I of this study, the temporal course H(t) and the daily mean H of the sensible heat flux H can be determined from measurements of the thermodynamic surface temperature (as a function of time) and from a one-time-of-day air temperature observation. Inaddition to these temperatures, one needs estimates of daily mean wind speed,of the roughness lengths of momentum and heat transfer, and of the displacementheight. In Part I, the algorithm was derived for areas with homogeneous surfaces,i.e., with uniform surface temperature, and the method was verified with measurements taken during several field campaigns. The root mean square error for the temperature difference between surface and air, in the comparison between measurement and model, amounted to one or two kelvin, and the error of H was 10 to 25 per cent. The method can be used to determine the sensible heat flux from measurements of surface temperatures by satellites, but can also be applied to ground based measurements.In Part II, the procedure is generalized for areas that consist of various surface types (sub-regions) with different surface temperatures, and can be usedwhen only a few (at least one) air temperature measurements per day are available over only one of the different sub-regions. This generalization should allow improvements to the estimates for H(t) by means of temperature measurements from, e.g., NOAA/AVHRR or LANDSAT/TM, taking into account the heterogeneity of the area contained in one METEOSAT pixel. Criteria are given as to whether effective (areal mean) surface temperatures and roughness lengths may be used for the computation of H or if the above mentioned generalized procedure has to be applied. The new algorithm is verified by measurements sampled during the field campaigns EFEDA 91 (Spain) and HIBE 89 (Hildesheimer Börde in Germany), and by using synthetic data (due to the lack of measured data) for one further combined surfacetype [soil and water (lakes)].